test: enable fixedbugs/bug193.go for -G compiler option

Temporarily disable a questionable test case in fixedbugs/bug193.go
and enable the test as a whole. See the issues below for details.

Updates #45114.
Updates #45117.

Change-Id: I1de6f8d79b592eeeec139cd92b6c9cac56a9a74b
Reviewed-on: https://go-review.googlesource.com/c/go/+/303094


Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>